Hydraulically supported rolls typically comprise a rotatable hollow cylinder forming a working roll circumference and a rotatably stationary crosshead extending lengthwise through the hollow cylinder to form an annular clearance space therebetween. The crosshead may have ends protruding therefrom to which external forces can be applied for supporting the roll, e.g., the ends may support the roll in a roll stand, calendar or similar support structure. Circumferentially spaced longitudinal seals are attached to the crosshead to abut the inner circumferential surface of the hollow cylinder. Axially spaced transverse end seals having a generally semiannular configuration are secured in respective circumferential slots in the two opposite ends of the crossheads such that they are secured in the circumferential slots against rotation and are displaceable in the action of the plane of the roll. The longitudinal and transverse end seals form at least one longitudinal chamber in the annular clearance space.
A sealing arrangement for hydraulically supported rolls is disclosed in DE-PS 11 93 739 wherein the longitudinal seal is in the form of a seal strip having an approximately L-shaped transverse cross-section. The longer leg of the "L" is supported in a longitudinal undercut or groove formed in the crosshead, while the shorter leg of the "L", which includes an end face that abuts the inner circumferential surface of the hollow cylinder, is oriented approximately perpendicular to a line tangent to the perimeter of the inner circumferential surface at a point of contact therewith.
Sealing arrangements incorporating such seal strips have been effectively used in floating rolls as disclosed in DE-PSA 10 26 609. Floating rolls have been developed to suitably perform in various applications. Such applications include those where the crosshead is subject to especially strong flexing forces due to high loading or a relatively small crosshead cross-section as disclosed in DE-PS 33 29 595. When subject to high loading or when the crosshead cross-section is relatively small, the crosshead may undergo excessive displacement at its center relative to the inner circumferential surface of the hollow cylinder. Such crosshead deflection leads to varying inclined positions of the L-shaped seal strip. L-shaped seals having a longer major leg have been used to limit this variation in the inclined position, which gives rise to edgewise contact of the shorter leg of the "L". The variation of the inclination of the seal strip is thus reduced during a certain radial displacement of the inner circumference of the hollow cylinder relative to the seal receiving longitudinal undercut in a direction perpendicular to the inner circumference.
The pressure of the pressure fluid in the longitudinal chamber biases the portion of the seal strips adjacent the inner circumferential surface of the hollow cylinder against the inner circumferential surface. The biasing force increases as the pressure in the longitudinal chamber increases. Therefore, although the sealing effect increases as the pressure in the longitudinal chamber increases, excessive contact pressure between the seal strip and the inner circumferential surface of the hollow cylinder may result, which may, for example, cause seal strip wear and premature seal failure. Furthermore, an increase in the cross-section of the L-shaped seal strips is accompanied by an increase in the pressure-effective contact surface of the seal strip and the hollow cylinder, and thus an increase in the contact pressure force acting thereon. Alternatively, the specific surface pressure in the contact area of the seal strip increases with an increase in contact pressure force. Accordingly, problems related to increased pressures in the longitudinal chamber may be exacerbated by increased seal strip cross-section.